Aqueous fabric conditioning compositions known in the art contain fabric conditioning agents which are substantially water-insoluble cationic materials having two long alkyl chains. The materials are usually in the form of an aqueous dispersion or emulsion and the addition of more than about 8% cationic material to the composition is not usually possible without incurring problems of physical instability.
There are many advantages to having more concentrated fabric conditioning compositions, for example there are shipping and packaging economies and the consumer can exercise choice in the type of performance obtained in that the concentrated product can be used as is or can be diluted to a conventional concentration before use.
Due to the desirability of formulating concentrated fabric conditioning compositions the problem of physical instability has been addressed in the art.
U.S. Pat. No. 3,681,241, Rudy, issued Aug. 1, 1972, utilizes a combination of quaternary ammonium softener, saturated imidazolinium softener, unsaturated imidazolinium softener and ionizable salts to formulate concentrated softeners, but the maximum concentration achieved is only 13%.
U.S. Pat. No. 3,954,634, Monson, issued May 4, 1976 uses a special batch processing technique of homogenization at high pressure to manufacture compositions comprising up to 15% fabric conditioning active.
The various solutions proposed, however, are not entirely satisfactory in that they either require the use of substantial quantities of materials other than the fabric softener in order to reduce the viscosity or in that special processing techniques are necessary to cope with the high viscosities generated which are not practical on a commercial scale or at concentrations above about 15% cationic conditioning agent.
The high viscosities generated during the manufacture of concentrated fabric conditioning compositions limit the quantity of composition that can be made using conventional batch processing equipment due to the large amounts of energy requirement for shearing the gel phases formed. This tends to mean that batch equipment is operated below capacity and with long cycle times. This leads to low throughputs which are not commercially attractive.
U.S. Pat. No. 4,439,335, Burns, issued Mar. 27, 1984 describes such a process. A mixture of cationic conditioning salts and an inorganic ionizable salt are used to make a concentrated aqueous composition. The composition is made in a batch process by adding a portion of ionizable salt to water concurrently with a molten mixture of the actives at a rate necessary to keep the aqueous mix fluid and stirrable. In one example, 200 lbs of product are made in a 60 gallon capacity main mix tank over a period of about 25 minutes.
There thus exists a need for a process for making a concentrated aqueous liquid fabric conditioning composition by a process which is practical on a commercial scale. There is also a need for a concentrated aqueous liquid fabric conditioning composition based on cationic conditioning agents which is physically stable and of acceptable viscosity.
Japanese Patent Application No. 63-77479 Yamamura/Kao, published Oct. 4, 1989 relates to a method of manufacturing a conditioning finishing agent in a line mixer by mixing water into a supply of molten quaternary ammonium salt. The agent is made by a single addition of water and the rate of production of the softening, finishing agent is only about 3 to 4 gallons per minute.
We have now found that it is possible to make an aqueous fabric conditioning composition of acceptable viscosity and stability by a continuous process that is practical on a commercial scale.